1. Field of the Invention
This invention relates to a display unit for vehicles, for displaying an image by an information display device, installed in a vehicle dashboard, to make a driver recognize visually, in an optimum field of vision for a driver.
2. Description of the Related Art
There is already such a display unit for a vehicle by prior art like one example, described in J.U.M. Application Laid-open No. H4-85370. As shown in FIG. 8A, this referred display unit has a display device 1 (liquid crystal display) for information data, installed in a dashboard 3 of a vehicle, and a displayed image by the display device 1 is reflected by a reflecting member placed under a windshield 4 to make a driver recognize visually.
This reflecting member is composed of a second polarizing plate 8. The second polarizing plate is placed under a windshield 4 and upper than a horizontal plane of a hood 5. A first polarizing plate 7, a polarizing direction of which is perpendicular to that of the second polarizing plate 8, is placed between the second polarizing plate 8 and the display device 1.
In this structure, a projected image by the display device 1 is reflected toward a driver""s eye position 6 by the second polarizing plate 8, passing through a prism 11 and the first polarizing plate 7.
External light, incident on the windshield 4 within range of angle xcex8, cannot reach to the display device 1 through the prism 11 and then does not deteriorate display device elements by lighting washout because the external light is shaded by the first polarizing plate 7 and the second polarizing plate 8 those polarizing directions cross perpendicularly to each other.
In a display unit for vehicles by prior art, the structure protects external incident light as mentioned above. There are, however, some display devices which project polarized light by themselves. A liquid crystal display, composing the display device 1 as shown in FIG. 8B, has a polarizing plate 1a on the top surface for required property and then, a projected light by a liquid crystal display is polarized by the polarizing plate 1a. If this polarizing direction is perpendicular to that of the polarizing plate 11a mounted on the prism 11, a projected light by the liquid crystal display can transmit through the prism, but its light power is attenuated by the polarizing plate 11a and then its display brightness remarkably goes down.
In the other hand, if adjusting the polarizing direction of the second polarizing plate for external light to the polarizing direction of a liquid crystal display, the second polarizing plate reflects vertically polarized light a little and then image quality is attenuated by bad influence of the reflective property.
This invention has been accomplished to overcome the above drawbacks and an object of this invention is to provide a display unit for vehicles, displaying a see-through image with high brightness and no ghost image at a better viewing position where can be recognized visually.
In a display unit for vehicles, according to this invention, comprising a display device for displaying information installed in a dashboard and projecting a reflective display image of the display device by a reflecting member placed under a windshield to make a driver recognize visually, the reflecting member has a prism placed above the display device, and a first polarizing means for reflecting the displayed image of the display device passed through the prism, toward a direction of a driver""s field of vision, and at least one of the display device or the prism has, on a surface thereof, a second polarizing means, a polarizing direction of which is perpendicular to that of the first polarizing means. The projected image by the display device is polarized perpendicularly to the polarizing direction of the first polarizing means by the second polarizing means, and inputted on the first polarizing means and reflected toward a driver""s field of vision. Since external incident light is polarized perpendicularly to the polarizing direction of the second polarizing means by the first polarizing means and external light incident on the prism is total reflected in the prism, the external light can be cut off into the display device.
The reflecting member, according to this invention, has the second polarizing means on the surface of the display device and then the projected image by the display device is polarized perpendicularly to the polarizing direction of the first polarizing means by the second polarizing means. The polarized image is projected into the first polarizing means through the prism. Since external incident light, polarized by the first polarizing means and going into the prism, is attenuated by the second polarizing means which polarizing direction is perpendicular to the polarizing direction of the first polarizing means and is total reflected in the prism, the external light can be cut off into the display device.
The reflecting means, according to this invention, has the second polarizing means on the surface of the prism and then the projected image by the display device is polarized perpendicularly to the polarizing direction of the first polarizing means by the second polarizing means when passing the prism. The polarized image is projected into the first polarizing means. Since external incident light, polarized by the first polarizing means and going into the second polarizing means on the prism surface, is attenuated by the second polarizing means which polarizing direction is perpendicular to the polarizing direction of the first polarizing means and is total reflected in the prism, the external light can be cut off into the display device.
In a display unit for vehicles, according to this invention, comprising a display device, installed in a dashboard, for displaying information data and a reflecting member, placed under a windshield, to make a driver recognize visually by reflecting displayed image of the display device, the reflecting member has a selfoc lens having prescribed limit incident angle placed over the display device, and a first polarizing means for reflecting the image of the display device, passed through the selfoc lens, toward a direction of a driver""s field of vision, and the selfoc lens has a second polarizing means on surface, which polarizing direction is perpendicular to that of the first polarizing means. Since external incident light is polarized perpendicular to the polarizing direction of the second polarizing means by the first polarizing means, and is absorbed by absorbing layer out of light transmitting area of the selfoc lens, the external light, incident on the selfoc lens, is cut off to the display device.
The selfoc lens according to this invention, which limit light incident angle covers the reflecting area of the first polarizing means, has total external light solution to cut off external incident light on the display device, since external light incident on inside area of the limit incident angle, polarized perpendicularly to the polarizing direction of the second polarizing means by the first polarizing means, is attenuated by the second polarizing means and external incident light from the outside area of the limit incident angle is absorbed by absorbing layer.
According to this invention, projected image by a display device is polarized perpendicularly to the polarizing direction of the first polarizing means by the second polarizing means and its image is inputted on the first polarizing means to be reflected toward a driver""s field of vision. Further, external incident light is polarized perpendicularly to the polarizing direction of the second polarizing means by the first polarizing means and external incident light on the prism is totally reflected in the prism. Then, since external incident light on the display device is cut off, high brightness image can be given.
According to this invention, projected image by a display device is polarized perpendicularly to the polarizing direction of the first polarizing means by the second polarizing means and its image is inputted on the first polarizing means through the prism. Further, external incident light, polarized by the first polarizing means and passing through the prism, is attenuated by the second polarizing means which polarizing direction is perpendicular and external incident light on the prism is totally reflected in the prism. Then, since external incident light on the display device is cut off, the image is reflected efficiently by the first polarizing means and high brightness image can be given.
According to this invention; projected image by a display device, passing through the prism, is polarized perpendicularly to the polarizing direction of the first polarizing means by the second polarizing means and its image is inputted on the first polarizing means. External incident light, polarized by the first polarizing means and going on the second polarizing means on the prism surface, is attenuated by the second polarizing means which polarizing direction is perpendicular and external incident light on the prism is totally reflected in the prism. Then, since external incident light on the display device is cut off and unexpected external incident light on the prism is prevented, clear image can be given.
According to this invention, image passing through the selfoc lens after projected by a display device is polarized perpendicularly to the polarizing direction of the first polarizing means by the second polarizing means and its image is inputted on the first polarizing means to be reflected toward a driver""s field of vision. Further, external incident light is polarized perpendicularly to polarizing direction of the second polarizing means by the first polarizing means and external incident light on the selfoc lens is absorbed by the absorbing layer out of light transmitting area. Then, since external incident light on the display device is cut off, high quality image with higher display height can be given in a smaller size compared with using prism.
In the selfoc lens according to this invention, the light aperture angle covers the reflecting area of the first polarizing means and external incident light on the aperture angle area is polarized perpendicularly to the polarizing direction of the second polarizing means by the first polarizing means and is attenuated by the second polarizing means. And external incident light over the aperture angle is absorbed by the absorbing layer. Then, since external incident light on the display device is cut off, thus total control for external can be done.